Phospholipids are an important constituent of all membranes, providing the milieu in which intrinsic membrane proteins may exert their influence. Drug molecules are thought to act on the intrinsic protein; however, the drug molecule must first enter the lipid region of the cell membrane and then perhaps undergo a conformation change in order to present the correct geometry for interaction with the protein. The medical applications of this work have to do with understanding a portion of the complex process of dug interactions with cell membranes. Techniques of one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy will be utilized to determine the conformation of the phospholipid and the drug, as well as any changes which occur upon complexation. The orientation of the drug within a phospholipid micelle or vesicle will be determined by 2D NOE (nuclear Overhauser effect) spectroscopy. This is the long-range goal of the project. The drugs used in the preliminary work will be the local anesthetics lidocaine and dibucaine, since their solution structure has been characterized. Micelles will be used in preliminary studies; the relatively narrow NMR lines for the phospholipids in micelles allows the measurement of spin-spin coupling constants. From the vicinal coupling constants the percentage of preferred conformation about dihedral angles may be calculated. The micellar work is also important for enzyme studies. The phospholipase enzymes are extremely sensitive to the aggregation of the lipid in the micelle, and therefore also to the conformation of the lipid head group relative to the acyl chains. The focus of this work is to uncover these conformational details.